When I spent a couple of days in and around London, I was amazed to see how obvious the speed cameras were, and even more interestingly, how they all had clear signs warning you that a speed camera was coming up.

Unfortunately outside of London it is a little different. Cameras are often hiden behind signs and trees.

Also we have roads that have camera warning signs every half a mile but no cameras.

Here in the US, you're lucky if you even see the cop with the laser gun when he nails you.

We have plenty of cops with laser guns here as well, it isn't all cameras.

I fairly religiously stick to 20, 30 and 40 limits, but I don't think cameras are the way to enforce them. Other limits I use as a guidance for my judgement. That doesn't mean I am always speeding though, you will regularly find me 20 or 30 mph under the limit if conditions dictate, when all the unthinking "I will drive at the speed limit, all the time" idiots are slavishly watching their speedos.